Finish remover compositions



United States Patent O 3,075,923 FINISH REMOVER COMPOSITIONS Neil W. Berst, Evanston, 11]., Wayne M. Gauntt, Los Angeles, Calif., and Eugene F. Maisel, Chicago, Ill., assignors to The Diversey Corporation, Chicago, 111., a corporation of Illinois No Drawing. Filed Dec. 11, 1958, Ser. No. 779,548 9 Claims. (Cl. 252-144) This invention relates to improved compositions for removing coatings from surfaces. More specifically, this invention relates to compositions for removing finish coatings such as paints, enamels, varnishes, lacquers and resins from coated surfaces. These compositions may be used for stripping such coatings from metal, wood, ceramic material, and the like.

Although the finish remover formulations hitherto known have in general been satisfactory for use in removing surface coatings of the common varieties of paint, varnish, and enamel, recent advances in the organic coatring industries have led to the development of new surface coatings having greater adhesion and greater resistance to softening and removal by the solvents commonly used for this purpose.

Most modern finish removers incorporate a chlorinated hydrocarbon as the principal solvent for softening and loosening the finish in order to permit its removal. These chlorinated hydrocarbons, a particularly preferred example of which is methylene chloride, do not have the dangerous flammability of the older solvents such as acetone, benzene, and petroleum naphtha and are therefore particularly desirable for this use. D

It has been discovered that the stripping ability of finlsh -remover compositions in which methylene chloride is used as the principal stripping agent is greatly increased by the presence of a small amount of a sulfonic acid activator selected from the group consisting of benzene sulfonic acid and alkyl benzene sulfonic acids, and preferably those alkyl benzene sulfonic acids wherein the alkyl group or groups contain a total of up to about 18 and preferably from about lto about 12 carbon atoms per molecule. These activators, used separately or in admixture in an amount of from about 0.1% to about 3,075,923 Patented Jan. 29, 1963 Thus the benzene sulfonic acid may contain no alkyl groups (as in the case of benzene sulfonic acid per se), one alkyl group (as in ethylbenzene sulfonic acid, hexylbenzene sulfonic acid, dodecylbenzene sulfonic acid, octadecyl benzene sulfonic acid, etc), or two or more alkyl groups, which may be the same or different (as in Xylene sulfonic acid, methyl isopropyl benzene sulfonic acid, d-iethyl benzene sulfonic acid, methyl dodecylbenzene sulfonic acid, etc.). The alkyl groups may be straight or branched chain and, in the case where two or more are attached to a single benzene ring, may be in any position (i.e., ortho-, meta-, or para-) with respect to each other. The total number of carbon atoms in the alkyl groups is likewise not critical and may range from 0 to about 17 or more. This is not to say, however, that all such alkyl benzene sulfonic acids are equally effective in activating the stripping ability of methylene chloride. It has been determined that themost effective are those in which the total number of side chain carbon atoms per molecule ranges from about 1 to about 12, and these acids accordingly constitute a preferred group.

The activating effect of the sulfonic acids of this invention on the stripping ability of methylene chloride in removing various modern surface finishes is demonstrated by the data in Table I. These data were obtained by tests carried out using mild steel panels which were given a preliminary cleaning in a solvent emulsion type cleaner, rinsed, phosphatized with an amorphous iron phosphate type of spray coating, rinsed, dried, and coated with each of several different types of commercially available modern finishes. The manufacturers directions for applying -an-d curing the finish were followed in each case. The panel was then placed in a container and covered with the finish remover. The time required for the bond between the metal and the finish to become sufficiently loosened to permit flushing off the finish with running tap water was noted. As standards for comparison, the same tests were performed using methylene chloride alone and methylene chloride containing a small amount of methanol which functions as a cosolvent to improve the homogeneity of formulations comprising methylene chloride and other ingredients.

Table I Surface Coating Removal Baked Epon Epon Urea Polyvinyl Baked Phenqllc Catalyzed with (Baked 350 F., Butyrate Finish Remover Composition, wt. Percent (200 F., 20 min.) primer (baked 20 min.) (air dried) 250 F., 10 min.)

Time, Removal, Time, Removal, Time, Removal, Time, Removal, min. percent min. percent min. percent min. percent 1 legliylene cglcrige"--- 13g 4 ..180 0 120 0 0 0 e yenec on e 2 Methanol m 6 180 o 180 0 180 0 180 0 Methylene chloride 85.2 3 hanol 10.2 20 25 100 5 100 15 100 Mixed crude xylene sul- 4. 6

ionic acids. Methylene chloride"..- 85.2 4 Methanol 10.2 30 100 30 100 7 100 15 100 Crude dodccyl benzene 4. 6

sulfonic acid.

20%, and preferably from about 0.5% to about 5% by weight of the total formulation unexpectedly improve extent that the removal of coatings which formerly could be accomplished, if at all, only with great diificulty using known paint strippers, now becomes a practical matter.

The sulfonic acids used as activators for methylene chloride in accordance with this invention are benzene the stripping ability of the methylene chloride to such an sulfonic acid and alkyl benzene sulfonic acids. The exact nature and size of the substituent alkyl groups is not important for purposes of the invention.

The above data clearly demonstrate that methylene chloride alone or combined with a small quantity of methanol was ineffective for loosening the surface coatings within a period of 60 to minutes. However, when the activators of the invention were added to the compositions these coatingswere entirely removed in 30 minutes or less. In addition to the ingredient serving the function of a solvent, such as methylene chloride, modern finish removing formulations usually contain a number of other ingredients, each of which serves a distinct and separate function. Among these are components generally designated as cosolvents, thickeners, and evaporation retarders. may be used to advantage in formulations containing such additional ingredients.

Cosolvents are used as aids in producing a homogeneous solution or stable suspension of the other ingredients of the finish remover. In some cases they may also assist in removing certain types of organic finishes from metal. Among the cosolvents which can be used in conjunction with methylene chloride and sulfonic acid activators of this invention are aliphatic alcohols such as methanol, ethanol, hexanol, decanol and the like; glycols, such as ethylene glycol, diethylene glycol, triethylene glycol and the like; aliphatic ether alcohols, such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, diethylene glycol monoethyl ether, diethylene glycol dimethyl ether and the like; esters, such as ethyl acetate; and well-known solvents such as acetone, dioxane, and petroleum ether. Other suitable cosolvents will be apparent to those skilled in the art. The cosolvent is generally used in an amount of at least about 1% and preferably about to about 40% of the total composition.

Finish removers which are applied by brushing or spraying, especially to vertical, inclined or underhanging surfaces, should contain a thickening agent in order to function with maximum eflectiveness. In the absence of a thickener the finish remover is very fluid and drains quiclo ly from the surface to be treated, so that there is insulfir cient solvent present per unit of area to penetrate the finish and loosen the bond between the same and the surface. By increasing the viscosity of the composition, the thickener prevents too-rapid draining and permits the remover to remain in contact with the surface for a sufficient time and in sutficient quantity to accomplish the desired loosening of the finish. Any material which is compatible with the other components of the finish remover formulation and which accomplishes the desired thickening can be used. Examples of typical thickeners include methyl cellulose, ethyl cellulose, bentonite, casein, and the like. Although thickeners can be used in amounts up to about 25% by weight to form a paste type of finish remover for special applications, they are commonly used in amounts of about 0.52% by weight of the total composition to form compositions suitable for general use.

Another usual component of modern finish remover formulations is an ingredient which retards the evapora- Coating The activators of the present invention 4 tion of the relatively volatile solvent used in the composition, thereby minimizing the costly loss thereof before the remover has had sufficient time to loosen the linish. A preferred example is paralfin Wax, typically having a Styrcnated Alkyd Butadiene Copolymer (water). Butadiene Copolymcr (solvent-s)- Acrylic Lacquer Phenolic (air dried) oxidizing Alkyd--. Oxidizing Epoxy Urea-Oxidising Alkyd (baked 325 F.).. Chlorinated Rubber Polyvinyl Acetate Styrene Butadiene Phenolic-pigmented (air dried) Phenolic (baked 200 F.) Epon.-- Epon-full primer (baked 350 F.) Epon-catalyzed and primer (baked 250 F.) Epan-phenolic (2 coats baked). Urea Melamine (baked 350 F.) Epon Urea (baked 350 F.) Silicone Alkyd Melamine (baked Nitrocellulose. Vinyl (baked 200 Vinyl orange (air dried Polyvinyl Butyrate- Phenolic Modified (baked 325 F.). II

5 melting point range of from about 12-0 to about 135 F. The usual range of concentration of these evaporation retarders in the formulation is up tov 20%, and preferably about 0.13% by Weight of the total composition.

In order to demonstrate the eiiectiveness of the activators of this invention in finish remover formulations containing additional ingredients of the types discussed above, compositions similar to modern commercial finish remover formulations were prepared and tested for effectiveness in looseningco-mmercially available surface finishes 15 from steel panels prepared as described in connection with the data of Table I. The formulations used in the tests had the following compositions.

Formula 1: Weight percent Methylene chloride 83.4 Methyl alcohol -c 5.4 Paraffin wax 1.4 Methyl cellulose 0.9 Dodecyl benzene sulfonic acid 6.9 Water 2.0

Formula 2: Weight percent Methylene chloride 61.2 Methyl alcohol 8.5 Paralfin wax 1.2

Methyl cellulose 0.8, Xylene sulfonic acid 8.6 Water 2.1 Diethylene glycol 2.4 Toluene 15.2

Also included in these tests for purposes of comparison was a composition similar to the above, but containing no activator.

Formula 3 (control): Weight percent Methylene chloride 91.5 Methyl alcohol 6.0 Paraflin wax 1.5 Methyl cellulose 1.0

Table II Formula 1 Formula 2 Formula 3 (Control) Time Re- Area Time Re- Area Time Re- Area quit-ed, Stripped, quired, Stripped, quired, Stripped, Minutes Percent Minutes Percent Minutes Percent 1 Runs discontinued at 30 minutes on indication of no film attack. By contrast, Formulas 1 and 2 showed evidence of film attack within initial 30 minute period.

Examination of the data in Table 11 indicates that Formulas 1 and 2, containing the activators of the inven tion, readily stripped, in reasonable periods of time, certain surface coatings (e.g., urea-oxidizing alkyd, eponfull primer, and epon-urea) on which the control formulation (Formula 3) was totally ineffective, even over prolonged periods. Moreover, the addition of the activators to these formulation had no adverse effect on their ability to loosen other coatings (e.g., styrenated alkyd, acrylic lacquer, and oxidizing alkyd) which were also readily stripped by the control finish remover.

It is therefore apparent that this invention provides improved finish remover compositions which are efiective in cases where the hitherto known removers fail, and which at the same time are just as effective as the latter for use on a wide variety of easily-removed coatmgs.

Although the finish remover compositions of the invention will in most cases contain a major proportion of methylene chloride, this is not necessarily always the case. Thus it is conceivable that for some special applications, the concentrations of thickener, evaporation retarder cosolvent and alkyl benzene sulfonic acid may total more than 50% of the total composition. Likewise, some other stripping agent may be used in conjunction with methylene chloride. The appended claims, however, are intended to cover those formulations in which methylene chloride is used as the principal stripping agent, i.e., in an amount greater than any other stripping agent, if any, which may also be present, regardless of whether or not the concentration of methylene chloride represents a major proportion of the total composition.

Although the invention has been described with reference to certain specific examples, these have been given by way of illustration only, and no limitation is thereby implied. Modifications and variations will be apparent to those skilled in the art.

What is claimed is:

1. A finish remover composition consisting essentially of methylene chloride and a minor proportion, suflicient to improve the finish stripping ability of said remover, of a sulfonic acid selected from the group consisting of benzene sulfonic acid, alkyl benzene sulfonic acids in which the alkyl groups contain a total of from 1 to about 18 carbon atoms per molecule, and mixtures thereof.

2. A finish remover composition consisting essentially of methylene chloride and from about 0.1% to about 20% by weight of the total composition of a sulfonic acid selected from the group consisting of benzene sulfonic acid, alkyl benzene snlfonic acids in which the alkyl groups contain a total of from 1 to about 18 carbon atoms per molecule, and mixtures thereof.

3. The finish remover of claim 2 wherein said sulfonic acid is dodecylbenzene sulfonic acid.

4. The finish remover of claim 2 wherein said sulfonic acid is xylene sulfonic acid.

5. The finish remover composition of claim 2 which includes at least about 1% of a cosolvent for said methylene chloride and said sulfonic acid.

6. A finish remover composition consisting essentially of methylene chloride, about 5-40% by weight of the total composition, of methanol, about 0.1-3% of paratiin wax, about 0.52% of methyl cellulose, and about 0.55% of a sulfonic acid selected from the group consisting of benzene sulfonic acid, alkyl benzene sulfonic acids in which the alkyl groups contain a total of from 1 to about 18 carbon atoms per molecule, and mixtures thereof.

7. The finish remover of claim 6 in which said sulfonic acid is dodecylbenzene sulfonic acid.

8. The finish remover of claim 6 in which said sulfonic acid is xylene sulfonic acid.

9. The method of removing films of paint, varnish, enamel, lacquer, and resin from a surface bearing the same which comprises applying to said surface a film softening amount of the finish remover of claim 1, allowing said remover to remain in contact with said surface until the film is loosened, and removing the loosened film.

References Cited in the file of this patent UNITED STATES PATENTS 1,700,491 Gravell Jan. 29, 1929 1,742,347 Fries Jan. 7, 1930 2,083,013 Freeman June 8, 1937 2,438,038 Graver Mar. 16, 1948 2,507,983 Kuentzel May 16, 1950 2,507,985 Kuentzel May 16, 1950 2,630,409 Bruner et al Mar. 3, 1 953 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No., 3,,075,923 January 29, 1963 Neil W, Berst et a1,

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 70 strike out "the stripping ability of the methylene chloride to such an" and insert the same after "improve" in line 64, same column 10 Signed and sealed this 3rd day of September 1963 (SEAL) Attest:

ERNEST w. SWIDER DAVID LADD Attesting Officer Commissioner of Patents 

1. A FINISH REMOVER COMPOSITION CONSISTING ESSENTIALLY OF METHYLENE CHLORIDE AND A MINOR PROPORTION, SUFFICIENT TO IMPROVE THE FINISH STRIPPING ABILITY OF SAID REMOVER, OF A SULFONIC ACID SELECTED FROM THE GROUP CONSISTING OF BENZENE SULFONIC ACID, ALKYL BENZENE SULFONIC ACIDS IN WHICH THE ALKYL GROUPS CONTAIN A TOTAL OF FROM 1 TO ABOUT 18 CARBON ATOMS PER MOLECULE, AND MIXTURES THEREOF. 